Let \(P\)  denote the maximum transmit power of each user. By employing the minimum mean square error (MMSE) combining and successive interference cancellation (SIC) techniques at the BS, the sum-rate for decoding the signals from all the \(K\)  users in bits per second per Hertz (bps/Hz) is given by [1]}
\(R(\mbox{{$ \Theta  $}})=\log _{2}\text{det}\left(\mbox{{$ I $}}_{M}+\sum _{k=1}^{K}\frac{P}{\sigma ^{2}}\mbox{{$ h $}}_{k}(\mbox{{$ \Theta  $}})\mbox{{$ h $}}_{k}(\mbox{{$ \Theta  $}})^{H}\right),\) 
